Method of copying



Patented Jan. 17, 1939 PATENT OFFICE METHOD OF COPYING Ludwig W. Wagner, Oak Park, Ill., assignor to A. B. Dick Company, Chicago, 111., a corporation of Illinois No Drawing. Application April 12, 1937, Serial No. 136,433

Claims.

This invention relates to a method of copying, and aims to provide a convenient and rapid method of producing duplicates from a master sheet bearing markings of soluble material and to eliminate the disadvantages resulting from the moistening of the impression sheets which has heretofore been necessary in making copies from such a master sheet. 5.-

In a known variant of the hectograph process, a paper master sheet is prepared by placing a piece of paper in'a typewriter with a reversed hectograph carbon sheet under it and typing the matter to be duplicated on the paper to offset from the carbon sheet to the under surface of the sheet of paper a mirror image of the matter to be reproduced. A master sheet thus prepared has on one of its surfaces, which I shall call its front surface, soluble markings usually consisting of a water-soluble aniline dye. Such sheets have been termed hectograph master sheets.

In reproducing copies from such hectograph master sheets, a number of impression sheets are brought successively into contact with the front surface of the master sheet. This has been done manually and in various types of duplicating machines.

In order to carry out this method of duplication, it is necessary that the soluble markings on the master sheet be dissolved as the impression sheets are passed in contact with the master sheet, so that a part of the dye in the markings may be transferred to each impression sheet. It has been the invariable practice to cause the necessary dissolving of the markings by moistening each impression sheet with a solvent for the dye, such as water or alcohol, before the impression sheet is brought into contact with the master sheet. This moistening of the impression sheets has led to distortion of the sheets, it necessitates delay both in the moistening and in the subsequent drying of the sheets, and it has proved so objectionable as to prevent any large commercial use of duplication from hectograph master sheets, notwithstanding the fact that the master sheets themselves may be made easily and with less expense than other means of printing or duplieating.

My invention eliminates these difficulties and. inconveniences by providing for reproducing copies from a hectograph master sheet without moistening the impression sheets. It thus provides a method of copying or duplication which is satisfactory and also very economical.

In accordance with my invention, the dye on a hectograph master sheet is dissolved by moistening the master sheet, instead of the impression sheets, with a solvent for the marking material. The moistening of a master sheet bearing soluble markings has heretofore been regarded as impractical. as this procedure would ordinarily 5 result in causing the dissolved markings to spread about on the surface of the master sheet so that nothing but a blur could 'be produced on the impression sheets. I have invented a method by which a master sheet bearing soluble markings may be saturated with a moistening liquid containing a solvent for the markings, without causing any spreading of the markings on the surface of the sheet. My method involves the use of a moistening liquid having a high viscosity, and the introduction of the liquid into the master sheet through its back surface. By a high viscosity as used herein, I mean a viscosity several times as great as that of water, and preferably amounting to at least five times that of water.

The moistening liquid passes through the master sheet from its back surface and completely saturates it, but its viscosity is so high that it does not drip from the front surface of the master sheet and does not wet the surface of an impression sheet brought into contact with the front surface of the master sheet, unless an unnecessarily heavy pressure is applied. At the same time, the liquid does pass into and dissolve the markings on the front surface of the sheet, and, when an impression sheet is brought against the front surface of the master sheet, the liquid carries a part of the dissolved marking material to the areas of the impression sheet lying directly opposite the markings of the master sheet.

I am not certain as to the reason that, although the liquid does not wet other parts of the impression sheet, it effectively carries a part of the dissolved dye into those portions of the impression sheet lying directly opposite the markings. This may be a result of the chemical affinity between the liquid and the soluble markings, or it may be because of the pressure between the impression sheet and the marked portions of the master 45 sheet, which project slightly from its surface. It is probable that both these factors enter into the result.

The high viscosity of the moisteningliquid, besides confining its action to the marked areas of the front surface of the master sheet, causes it to enter into the soluble markings slowly. For this reason, the liquid causes a gradual dissolving of the dye while the impression sheets are being successively passed in contact with the master sheet, so that some of the dye is transferred to each impression sheet.

In order that a large number of copies may be produced before the dye on the master sheet is exhausted, it may be desirable to make the viscosity of the moistening liquid higher than that which is required merely to prevent dripping and blurring, in order that the viscosity of the liquid may materially retard the dissolving of the dye. For this purpose, a viscosity above ten times as great as that of water is desirable; but the viscosity should not exceed twenty-five times that of water, as such excessive viscosity does not permit sufficient penetration to allow successful practice of my method.

In addition to having a solvent action on the dye and a high viscosity, the moistening liquid should be a permanent liquid, that is, one which does not change its characteristics on standing. It may consist of a single chemical compound which is not volatile, or of a mixture of chemical compounds which are sufficiently compatible to avoid separation on standing, and none of which is volatile. The moistening liquid may consist of a singlesolvent having a high viscosity, or of a mixture of solvents, or of solvents and non-solvents so chosen that the viscosity of the mixture is high.

Illustrative examples of suitable moistening fluids are as follows:

Example I Ounces Diethylene glycol 1% Glycerin 2% Example II Ounces Diethylene glycol 1% Glycerin 2 Oleic acid Triethanolamine Example III Ounces Diethylene glycol 1 Oleic acid 1 A; Triethanolamine l The viscosities of the moistening liquids of the examples, compared with that of water, are as Example III 22.4 times that of water The viscosities were determined on the Stormer viscosity meter at 21.8 C. and compared with that of water determined in the same way. Of the ingredients specified in the examples, diethylene glycol and glycerin are solvents for aniline dye. Oleic acid and triethanolamine are nonsolvents. They increase the viscosity of the moistening fluid and serve to delay the dissolving of the markings.

The moistening liquid is introduced through the back surface of the master sheet by pressing the back surface of the master sheet against an absorbent pad saturated with the moistening liquid. The impression sheets are brought successively into contact with the front surface of the master sheet under gentle pressure, while its back surface is pressed firmly against the pad.

In the practical carrying out of the method, the pressing of the back surface of the master sheet against the pad and the bringing of the impression sheets successively into contact with the front surface of the master sheet may be effected manually. But, in order to obtain the full advantages of the invention, which include making possible the taking of copies with great rapidity, it is desirable to use some form of simple mechanism as an aid in carrying out the process. Any usual stencil duplicating machine may be used by merely substituting my impregnated pad for the ink pad of the machine, and attaching the master sheet over the pad by the devices provided for attaching a stencil over the ink pad. When a considerable number of copies are required, additional moistening liquid may be applied to the pad while the copies are being made.

} This may be effected in the manner in which ink is applied to the ink machines.

What I claim is:

pad in stencil duplicating 1. In the method of reproducing copies by' bringing successive impression sheets in contact with the front surface of a master sheet having markings of soluble material on its front surface, the step which comprises passing through the master sheet from its back surface a stable liquid having a dissolving action on the marking material and having a viscosity more than five times as great as that of water.

2. In the method of reproducing copies by bringing successive impression sheets in contact with the front surface of a master sheet havin markings of soluble material on its front surface, the step which comprises passing through the master sheet from its back surface a stable liquid having a dissolving action on the marking material and having a viscosity which is between five and twenty-five times that of water.

3. In the method of reproducing copies by bringing successive impression sheets in contact with the front surface of a master sheet having markings of soluble material on its front surface, the step which comprises passing through the master sheet from its back surface a stable liquid having a dissolving action on the marking material and having a viscosity from ten to twenty-five times that of water.

4. In the method of reproducing copies by bringing successive impression sheets in contact with the front surface of a master sheet having markings of soluble material on its front surface, the step which comprises passing through the master sheet from its back surface a stable liquid containing a solvent for the marking material and a non-solvent for the marking material which delays the action of the solvent on the marking material.

5. In the method of reproducing copies by bringing successive impression sheets in contact with the front surface of a master sheet having markings of soluble material on its front surface, the step which comprises passing through the mastersheet from its back surface a stable liquid having a viscosity more than five times as great as that of water and containing a solvent for the marking material and a non-solvent for the marking material which delays the action of the solvent on the marking material.

6. In the method of reproducing copies by bringing successive impression sheets in contact with the front surface of a master sheet having markings of soluble material on its front surface, the step which comprises passing through the master sheet from its back surface a stable liquid containing a high-viscosity solvent for the marking material and a non-solvent for the marking material which increases the viscosity of the liquid.

7. In the method of reproducing copies by bringing successive impression sheets in contact with the front surface of a master sheet having markings. of soluble material on its front surface, the step which comprises passing through the master sheet from its back surface a stable liquid 9. A liquid for introduction into a hectograph master sheet for making copies therefrom consisting of a mixture of a non-volatile solvent for the dye on the master sheet and a non-volatile ingredient serving to delay the action of said solvent, said mixture having a viscosity between five and twenty-five times as great as that of water.

10. A fluid for introduction into a hectograph master sheet for making copies therefrom consisting of a permanent substantially non-volatile, substantially non-separating liquid mixture of a non-volatile solvent for the dye on the master sheet and a non-vo1atile ingredient serving to delay the action of said solvent, said mixture having a viscosity between five and twenty-five times that of water.

LUDWIG W. WAGNER. 

